JCB Interview Questions and Answers

Calling a function using the new keyword creates a new instance of the function's constructor.

• Creates a new empty object

• Binds 'this' to the new object

• Adds a property to the new object called '__proto__' which points to the constructor function's prototype object

• Returns the new object

You can import all exports of a file as an object in JavaScript using the 'import * as' syntax.

• Use the 'import * as' syntax followed by the object name and 'from' keyword to import all exports of a file as an object.

• For example: import * as myExports from './myFile.js';

• You can then access the exports using dot notation, like myExports.myFunction().

The 'this' operator in JavaScript refers to the current context or object.

• Refers to the current object or context in which a function is being executed

• Can be used to access properties and methods of the current object

• The value of 'this' is determined by how a function is called

Observables are streams that can emit multiple values over time, while promises can only emit a single value.

• Observables can emit multiple values over time, while promises can only emit a single value.

• Observables are cancellable, while promises are not.

• Observables support operators like map, filter, and reduce for transforming data streams, while promises do not.

• Observables are lazy, meaning they do not run until they are subscribed to, while promises start executing as soon ...read more

Arrow functions are a concise way to write functions in JavaScript.

• Arrow functions are defined using the '=>' syntax.

• They have a shorter syntax compared to traditional function expressions.

• They do not have their own 'this' keyword, instead they inherit it from the parent scope.

• Example: const add = (a, b) => a + b;